Question 223619
9 – 4a ≤ -3 
-4a<=-3-9
-4a<=-12
a>=-12/-4 (note: when dividing by a negative value the < sign changes to a > sign).
a>=3 ans.
Proof:
Let a=3.1
9-4*3.1<=-3
9-12.4<=-3
-3.4<=-3